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Jess8bit
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Copy that !  what is wrong with the double coating ? delamination ? the two coats can't bind so well ?
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wozza
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[quote] Jess8bit (11/06/2013)
Copy that ! what is wrong with the double coating ? delamination ? the two coats can't bind so well ?[/quote Yep. And also if the coat is too thick then it has an effect on how the carbon looks after infusion. Hard to explain but it becomes a little "fuzzy-blurred" looking. More noticeable on 2/2 Twill than plain weave. Aim for one coat about 0.2mm thick, it takes some practice but you will get there I did some testing to get it right. Put some release agent on a piece of glass, mask off some strips on the glass, spray on some GC50 adjusting the air pressure and distance the gun is away from the surface etc (make notes obviously and number the strips as you spray them. Once fully cured you can measure the thickness of each strip with a vernier or micrometer. Thickness of each strip minus the thickness of the glass. Hope that makes sense. Warren
Carbon Copies Ltd
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Jess8bit
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That really makes sense. I did not yet touch the pressure tuning knob on the gun. I only set the compressor to 80 psi. And spray from around 40cm high. Feel quite unconfortable with it
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wozza
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Jess8bit (11/06/2013)
That really makes sense. I did not yet touch the pressure tuning knob on the gun. I only set the compressor to 80 psi. And spray from around 40cm high. Feel quite unconfortable with it Set the pressure with the spray gun attached and the trigger fully depressed. Gelcoat guns use a lot of air. If you just set the regulator on the compressor to 80psi depending on the size/delivery of your compressor you won't get anywhere near that psi at the gun. I have attached a pic. When you get it right GC50 is brilliant. That is straight from the mould with just a quick wipe over with "panel wipe" to remove the release agent. 
Carbon Copies Ltd
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Jess8bit
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The spray seems strong to me (almost too much I'd say, but only a feeling though). My compressor is a Michelin 3hp 100L. Here's how it looks after spraying. Maybe too thick this time (was afraid of missing a spot ^^). By the way I don't know how to calculate the amount of GC to prepare, for a given surface. And can't get rid of these blobs, I'll have to sand them. |
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wozza
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Not easy to tell from those pictures but you dont' appear to be a million miles away. The "blobs" are simply from the tip. When you stop spraying gravity is still forcing the gel coat to the tip of the gun. If you wait too long before commencing spraying a "blob" of gelcoat will drop "plop" in the middle of the part. Or when you start spraying again that "blob" will go "splat" over the surface of the part. Some tips- start spraying away from the mould surface and then move over it. Once spraying and over the mould continue spraying, no stop starts this will create drips. If you have to stop spraying, only release the trigger once off the mould surface. Keep a piece of kitchen towel in the hand not operating the gun. As soon as you stop spraying cover/wipe the tip with the towel and keep it there until you commence spraying again. I think I may have to start charging for all these "trade secrets" Lol
Carbon Copies Ltd
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Jess8bit
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^^ yeah, those are very valuable tricks, I really appreciate you sharing those, thank you !!! sorry for the photos, each time I upload them they are considerably resize although originals are big enough to see the details.
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wozza
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No problem I was only joking, happy to help. Carbon is expensive and given the time element it can be VERY frustrating and rewarding at the same time. It is the CFM of your compressor that is important. If it is continuously trying to keep up with the demand of the spray gun then you will get fluctuations in the pressure/volume of air being delivered. You really need a minimum of 12 CFM. But these requirements will depend upon the area of the mould surface you are spraying. Also the size (bore) and length of the air line/hose you are using will make a big difference. Keep the hose as short and as big a bore as you can. 1/2" NB if possible.
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Jess8bit
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mmm, 'm bit disappointed about my compressor, thought it was well dimensionned, but it has the following specs :input air : 350 liters/mn.
output air : 270 litres @ 7 bars.
Seems it is below the 12cfm required. Guess it won't go for a car bonnet :-/
my line is 10 meters long, and I have to check the diameter yet.
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wozza
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Your compressor may well be ok for a bonnet? just make sure you only spray a small area at a time, giving the compressor chance to keep up. What I am saying is if you over stretch the compressor you will get a difference in the thickness/texture of the gelcoat you are laying down. On something like a bonnet that will be noticeable in the surface finish once infused.
Carbon Copies Ltd
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